Means and method for stimulating the flow of well fluids and for declogging well bore walls and well casing perforations



N. A. MacLEQD April 3o, 1957 MEANS AND METHOD FOR STIMULATING THE FLOWOF WELL FLUIDS AND FOR DECLOGGING WELL BORE WALLS AND WELL CASINGFERFORATIONS 2 Sheets-Sheet 1 Filed April 2l, 1949 @EAR/N6 STRA TA April30, 1957 N. A. MacLEoD 2,790,388

MEANS AND METHOD FOR STIMULATING THE FLOW OF WELL FLUIDs AND FORDECLOGGING wELL BORE wALLs AND wELL CASING PERFORATIONS Filed April 21,'1949 2 Sheets-Sheet 2 IIIII.

4 L l A .A M M MEANS AND METHD FR STIMULATING THE FLOW F WELL FLUIDS ANDFR DECLOG- GING WELL BORE WALLS AND WELL CASING PERFDRATIONS Norman A.MacLeod, Altadena, Calif.

Application April 21, 1949, Serial No. 88,818

7 Claims. (Cl. MIZ-21.6)

This invention relates to a means andV method for stimulating the ow ofwell fluids and for declogging Well bore walls and well casingperforations, and involves mainly the production of a series ofvibrations or pulsa# tions in or about the well or well strata, theperiodicity of the pulsations being controllable both as to quality andquantity over any desired period of time, great or small, ranging frommicroseconds or milliseconds to seconds, minutes, or more, and thetotality of the pulsations being as great as desired.

This invention involves the production of a series of shock waves tothereby produce regular or irregular and continuous vibrations in thedesired location, such vibrations to be produced by a series ofexplosions or by other suitable means for producing periodic vibrations.

It is well known that the casing perforations commonly used throughoutthe bearing strata in oil, gas, and other wells, tend to become cloggedwith clay, sand, shale, paraiiin, cement, corrosive incrustations, andthe like, greatly reducing and sometimes entirely shutting offproduction from the well.` Paraffin or 'asphaltum often accumulatesinside and outside the casing, as well as in the perforations, alltending to stopY the inflow of well fluid.

, And as time goes on, the productive formation immediately outside theperforated casing accumulates parafn, asphaltum and the like, becomestightly packed, hard, and of little or no porosity, thus forming animpermeable barrier about the casing.- In fields in which the productiveformation is not of a crumbling nature, the well hole is often uncasedin the productive strata. While in such wells there are no casingperforations Vtobecome clogged, the walls of the hole accumulatep'araiiin, asphaltum, and the like, which ll and choke the pores of theformation and greatly reduce production.

When production from the well decreased materially due to suchconditions, Washing and cleaning operations must be undertaken. However,known methods for washing and cleaning the perfor-ations by outward flowof Huid are not always fully effective, and even though they maysometimes succeed in breaking the clogged casing perforations, they arenot always effective to open or clean the tightly packed or cloggedsurrounding formation. VMoreover, the perforated section of the casingmay be from a hundred feet to fifteen hundred or more feet in length,and the job of washing and cleaning by the conventional methods incommon use at the present time is a heavy and time consuming operation.

According to one common present practice of perforation cleaning,successive zones of the perforated section of the casing are packed olf,and water is forced out through the perforationsbetween the packers, thefull length of the perforated section of the casing being cleaned arelatively few feet at a time. This practice Vhas several seriousdisadvantages and shortcomings, some of which may be enumerated; iirst,numerous successive operations are required to cover the length of theper forated casing; second, the wash water tends to escape States Patentwash water.

y 2,790,388 Patented Apr. 30, 1957 through perforations that are alreadyopen, and often does not break tightly clogged perforations; third, thewash water does not open up the clogged formation outside the casing;and fourth, the wash water is incapable of removing any substantialproportion of the accumulated parain or asphaltum, which is insoluble inthe HotV water or steam, hot oil, and sometimes acids, are used in aneiort to dissolve and carry off the parain and asphaltum deposits inboth cased and uncased wells, but usually with little or incompletesuccess.

In the past explosives have been used for the same general purposes, butwhether thereA are a number of individually spaced explosive charges, asin Patent No. 2,362,829, or an explosive cord extending throughout thedesired location, as in Patent 2,414,349; there is a substantiallysimultaneous single explosion produced, with but a single compressivewave followed by a single rarefication wave. This though, is like one,attempting to clean a small clogged tube, would hit it with a singleblow of a hammer. With this invention, a series of explosions arecaused, microor milli-seconds apart, as desired, causing a series ofalternate compression and rareication waves or pulsations. This is likeusing a pneumatic hammer to clean the small clogged tube, wherein theperiodicity of the hammer is controllable, as desired, thus setting up aseries of vibrations and causing a thorough shaking or jigging etect,and providing a complete declogging action.

A further object of this invention is to cause periodic or intermittentexplosions to produce a series of shock waves and thereby providecontinuous vibrations over a period in the ground or in any structure. K

A further object of this invention Vis to provide the use of controlledexplosions at diierent controllable time intervals to producepulsations, such control involving the spacing of the explosions; theamount of explosive at each spaced location; the type of explosives; andthe timing of the explosions to thereby produce'any desired quality andquantity of shock wave series over any desired period of time. t

A further object of this invention is to provide a controllable seriesof shocks to produce jarring effects on materials other than earthstructures, such as for instance, in loosening a drilling tool which isjammed in the well hole, or in freeing a well casing which is frozen inthe bore when the casing is being salvaged. v

A further object of this invention is to use a controllably timed seriesof explosions in the well or on the ground adjacent to a well or wellsto stimulate the flow in one well, or in the one well and in adjacentwells.

A further object of this invention is to provide a means and method ofsetting a controllably timed series of explosions in a well, whereineach individual explosive charge, or group of explosive charges, may beset off individually without simultaneous setting off of the otherexplosive charges 'already present in the well, and without disruptingthe control means Vto, such other explosive charges. y

A further object of this invention is to provide a method and means ofcentralizing the explosive charges with the well and of spacing andcentralizing such charges below a pump or other obstruction already deepwithin the well without the expense or necessity -of rst removing thepump or obstruction from the well. 'l Y Further, this invention isconcerned particularlyY with methods of and means for stimulating ow ofliquids from wells producing water, brine, oil, or sulphur (by theFrasch process), but generally the invention can be used in anyapplication where a series of high energy pressure pulses canybeusefully applied to produce Vibration, or to cause a series of pressurewaves and a series of interactions from these pressure waves to affectthe character of the medium in and throughV which they may be traveling.

In the particular case of .oil wells, pores of the strata not onlyadjacent to but also for a considerable radius around the perforatedwell lcasing become kclogged due to the iiow of liquidrcarrying smallsolid-particles. After initial ilow, therefore, a tendency to lowerdelivery rate occurs due to this effect of interatices in the strataYbeing clogged by such solids. In particular in heavy-oil wells, due tohigh viscosities of the fluids, a considerable movement of lfine solidparticles may occur in the vdirection of low and settle intheinterstices of 'grains and even againstaud in the well casing.

The effecting of diminishing flow iniuseis :also produced by clogging ofthe Vperforations by solidiaccretionsatjthc perforation by .physical'and chemical action.

In the methods cited in APatent's25414;349 and 2,362; 829, it isindicated that ,substantial :simultaneity tof 'effect is produced. ,-InPatent 2,414,349, etectually one pulse of pressure .is produced,ftheffrontoffwhich :bears -a slight angle 'to .the -faxis .ofv thecasing vin which the primacord is contained, which is inclined upward ordownward from the axis accordingly, as theprimacord -is detonated fromthe bottom or Vtop of the length used. In the 'method disclosed inPatent 2,362,829, the simultaneous detonation of multiple charges causessevere llocal pressure build-up by a VDautrische eiect when -two shockwaves from adjacent charges in the liquid collide. -In both Patents2,414,349 and -2,362,829the substantial simultaneity of detonation ofthe explosive used does two adverse things: (a) The total explosiveenergy `is delivered to the pipe in a very short time, hence vthere is alimit in the amount of explosive which can tbe used in such a pipe ifthe pipe is not to be ruptured 'or vseverely damaged. Even withprimacord containing only 3.0 grains?. T. N. per foot, the -explosive isset olf at the rate fof almost 90 lbs. per second, which can be, in thecase `of some casings in water Wells, too high an energy delivery rate.(b) A substantially single pressure pulse is transmitted through theadjoining strata or rock formation.

The use of a ysingle pressure pulse is not so elective as a multipleeffect in which lsucceeding pressure waves travel through previouslydisturbed material which may not have 'come vto rest, lthereby causing ajigging action to greatly increase the de-clogging and flow-stimulatingeffect.

Other additional objects will more fully appear from the followingdescription, and that y"thelinvent'ion may be more fully understood,reference'is had to the accompanying dra-wings forming a part of thepresent descripe tion and-illustrating preferredenlbodirnents of theinvention, in which:

Fig. l is a schematic view 'of one form of the invention in position inan oil well;

Fig. 2 is a sectional view showing a different form of contact control;

Fig. 3 is an enlarged detail of the explosive supports, and cableprotectors;

Fig. 4 is a section on line 4-4 of Fig. 3;

Fig.V 5 is a modified form of explosive support and cable protector;

Fig. 6 is a side view of Fig. 5;

Fig. 7 is a sectional view online 7-,7 of Fig. 5;

Fig. 8 is a sectional view on line 8,-8 of Fig. 9;

Fig. 9 is a fragmentary elevational view of another form of explosivesupport;

Fig. 10 is aschematic view of anotherfon support; and'v s Fig. ll is aschematic view of an arrangement of the explosives. Y

This invention involves the Ydetonation of aimultiplicity of explosivecharges 10 distributed lalong the well 11 of Vexplosive i Vwithin theoil bearing strata 12 wherein is :located the strainer portion 13 .ofthe well Ycasing v11i. Thecharge's 4 10 are suspended in the well 11 bymeans of multiple conductor cable 15 having a plurality of spacingspring fingers 16, at least two or more, interposed between each of thecharges 10 to space the cable, and thus the charges, from the sides ofthe well and retain it along the axis of the well.

As shown in Figs. 3 and 4the explosive charge 10 includes a pair ofexplosive elements 17, each supported on an arm 13 extending from 'theJrniddle -ar-m 21 of a steel guard 20. This middle arm l21 is hollow,the Vcable 1S extending therethrough and thus supporting it, and ishexagonal `in cross-section, -and `of greater thickness than that of theexplosive element 17, so that when one of the explosive elements 17 isdetonated V'by the electric charge from the leads L22lextendin`g fromcable 15, the explosive force is directed away from the cable 15, aswell as the other explosive elements 17 the other side fof 'the samesteelzguard 2t).V This 'steel guardli),

it will be noted, is shaped like a .figure S lying on eits side', andl.the outer arms 2 3 thereof likewise have Aan angular -face 24011 theside toward `the 'explosive .element 17 to help divert the explosive.force therefrom While the leads 22 are diagrammatically shown asextending directly from :the cable 1S, it :is obvious that such leadscan -extend through the supporting arms 18, so long as they are properlyarmored to prevent the shock wave from the explosion from disrupting thecable 15 within the guard arm 2-1.

This invention also involves means for detonating the explosive elements-17 at definite -time intervals and patterns of events, as, forinstance, successively within the elements along 'the well axis,alternately, `every third detonator, or any combination andpermutationof aflarge number so possible. Both elements 17 of the samechar-ge 10 might be detonated simultaneously, or one element 1:7 mightbe part of one group, and the other part of another or alternate group.The various patterns are made possible by :the provision of themulticabie .15, each sub-cable therein having a lead 25 going to anindividual contact 26 which cooperates with switch arm contact 27 on vanarm 23 rotatable by a inotor shaft 30 in a bearing 31 on a motor 32,Ywhich is controllably operated at ya desired-,speed from .any suitablesource of power. The contacts 26 are arranged in an are of a circle;suitably spaced from eac-h other and withrelation to .fthe speed ofrotation of the arm contact 27 over the individual contacts 26 so Vthatthe circuits will be completed t'o the individual contacts 26 atithevdesired number ofmilliseconds. Then, when `the switchV S isoperated to complete the circuit from the battery B through the returnwire 33, a spark is created between the ends of the leads 22 in each 'ofthe various individual explosives 17 sto Adetonate them in thedesiredpattern and the desiredsequence, to thus se't Voli? a series ofexplosions properly timed from each other to provide ya desired sequenceof shock waves causing a pulsation of compression andH rareficationwaves throughout the desired areas of the well and of the surroundingstrata, thus simulating the effect of a pneumatic hammer, rather thanasin the prior art, that of a single blow of a hammer.V The Vpulsationthus set up will have the eifect of flushing the liquid normally presentin a well back and forth kthrough the strainer perforation and throughthe interstices of the strata thereabout, thus ee'ctively cleaningVsuch. interstices and `stimulating the Y ow of the well 4luidtherethrough. Such pulsation will s have kthe Veffect of providingr acontinuous shaking or Vsingle blow. Further, Vinasmuch, as a continuousshaking jiggling of the well and the strata, rather than merely a y o isfar more leffective than afsin'gle blow, the individual blows may bemuch gentler than is -necessary in the case of a single blow, and theindividual explosive elements may be much smaller in quantity andexplosivel force than when only a single blow s provided, hence theindividual blow or force of the individual charge may be kept wellwithin the safety'limit. thus avoiding any danger of collapsing eitherthe well or of the well casing.

In Fig. 2, there is shown an alternate means of completing the circuitsto the multicable at the desired timing. In this form, the contacts 26are arranged in an insulation cylinder 29 and connect the leads 25' fromthe multicable 15 through the piston contact 28 and shaft 31 to batteryB' and returns wire 27'.

In Figs. 5, 6 and 7, there is shown another form of explosive charge 10.In this form, the steel guard 20' is substantially `D-shaped and itsarms 21 and 24' are each provided with angle faces 23', between which issup ported the individual explosive element 17 depending from an arm i3'through which the leads extend from t-he multicable supporting conductorIn Figs. 8 and 9, there is shown another type of explosive support. Inthis form, a series of explosive cords countersunk in spiral grooves 36in a rod 37 of a length suitable to the depth of the area to bestimulated. If the depth of the area is too great for a single rod 37,

suitably joined rods, one suspended on another by a suitable exiblejoint, provide flexibility as the rod is run in the well. The cords 35may be detonated by an arrange- .ment like that already described toprovide a series of explosions, eight with the rod as illustrated.

When it is desired to provide a series of pulsations in a well having apump 41 operated by a sucker rod 42 or otherwise, which it is notdesired to remove because of the expense and time of so removing andreplacing it,then a form may be used as shown in Fig. l0, this form alsobeing useable in any type of well. In this form, fthe multicable 43 islowered along one side of the Well casing 44, being pressed thereagainstby the somewhat S-shaped leaf springs 45 secured at one of their ends 46tothe multicable 43, while their free ends 46 press against the oppositeinner side of the casing 44. At their mid points, each spring finger 45carries an individual explosive element 47 connected by leads 4S to themulticable 43. When the cable 43 is lowered, its end will pass throughthe circular or newmoonshaped space about the pump, and the springfinger 45 will flex, as at 45', to bypass the pump, the explosiveelement being in the form of a at disc thin enough to bypass the pump.When the pump 4l is bypassed, the lingers spring back to their originalshape, holding the explosive elements 47 as substantially axially of thewell casing 44 as is permitted by the pump suspending sucker rod 42. Dueto the number of individual charges that may be used, each individualexplosive element is so comparatively small that no damage will resultto the pump or its operating mechanism, yet with the multiplicity ofpulsations set up, a thorough cleaning is easily provided, both of thewell strainer perforations and of the surrounding strata to thus greatlystimulate the ilow of the well lluids.

Fig. 1l shows diagrammatically how a substantially indefinite number ofcharges 50 may be provided on a cable 5l in a well casing 52 within awell stratum 53. As shown, a hundred or more individual charges 50 maybe provided. Using the ten contact cable of Fig. l, the numerous chargescould be set off in any desired ten groupings, such as 1, l1, 21, etc.;2, 12, 22, etc. Also, the groupings may be of different sizes, ifdesired, thus one grouping being live in number, then ten in number,

then ve in number, etc., all made up and varied according to theparticular conditions of the well.

As a result, it can readily` be seen that as far as functioning ofcombinations only the number'of explosive charges and number of leadslimit the'variations of tiring sequences and arrangements. val betweensuccessive tiring of single explosive charges or groups of charges canbe varied at will, allowing great flexibility of operation so thatpulsing can occur at millisecond, hundredth second or any otherinterval.

The advantages of therinvention are: v

(l) That by detonating a series of explosive charges v of detonationsvariously spaced in the casing and in a time period produces anextremely effective clearing action and is well known and practiced inordinary life, when, for instance, a multiplicity of impacts to free aclogged instrument is often better than a single blow.

(4) That the interaction of pressure waves arriving from different lociin a casing at any other point in the casing or adjoining strataproduces Va modified Dautrische effect which greatly enforces thepressure at that point. Such enforcement of pressure travels outwardwith the interacting pressurev waves and produceszoneinthe strata inwhich an augmented eifect is produced'.

(5) If succeeding pressure waves are produced Vin symmetrical sequencefrom' regularly spaced charges, the zones of high pressure `described in(4) are traversed by ,y succeeding interaction points and so may produceflow In all cases the time interlines and even'structural breaks in thestrata at these zones.

(6) 'Ihe energy delivery rate of -any series of explosive chargesarranged on a cable by a standard production method can be changed atthe point of application as desired to adjust to the eect desired and tothe strength of the casing.

(7) In every well containing casing of diterent strengths, it ispossible to use different energy delivery rate to different lengths ofwell casing.

(8) The use of .a relatively large amount of explosive and the enhancedeffect of a persistent series of pressure pulses through =a stratum, canso break down clogging conditions in the stratum, that the flow ofliquid in adjacent wells will be improved.

In the same manner that the cable 43 with its spring inger 45 andexplosives 47 may pass lthe pump 41, it may likewise pass along adrilling tool jammed in the well bore and be operated to jar the toolloose. Likewise, any other structure, whether in a well or otherwise,may be vibrated and loosened by the means and method of this invention.

Obviously, the length of duration of the continuousV pulsations may bevaried as desired, by merely using an appropriate number of explosivecharges on the string. If desired, additional explosive charges can befed to the operation area continuously at a desired rate consistent withthe desired periodicity of the pulsations.

While the invention has been described with reference to certainspecific illustrative means for carrying it into eiect, it will beunderstood, however, that various changes in design, structure andarrangement may be made, without departing from the spirit and scope ofthe invention, or of the appended claims.

What is claimed is:

l. A string of explosive charges arranged to be run Vinto a deep welland to bypass a partial obstruction present therein, said stringcomprising a supporting and detonating cable, a plurality of flexiblesupporting arms, each of said arms having its central portion connectedto a separate one of said explosive charges and being secured at one endto sai-d supporting cable toA normally spaanse spring of greater -lengththan 1the diameter ofthe deep Well, said 'leaf spring 'being Asecured4at V:one end to 'said supporting 'cable `t`o no'rnrallyex'tendsor'newhait radially therefrbnrpand arranged to temporarily yield towardthe cable axis as the obstruction is being bypassed and then returnktoward vnormal position, andan explosive element Vsecured lmidway ofeach leaf 'spring `t`o beheld substantially axially ofthe Well when indetOn'ating-,position 3. A string of explosive charges arranged to berun into a deep wll and :to bypass a partial bpstrncfien presenttherein, said string comprising av supporting and detonatingcab'le, each'explosive charge including a leaf spring of greater length. than 'thediameter of the deep welL'said 'leafspringfbeing secured at one end tolsaid supporting cable 'to normally extend somewhat radially therefromand arranged to temporarily `yieldftoward the c'abl'e'axis as 'theobstruction is being 'bypassed andthen return "toward normal position,anexplosive element secured midway "of ea'ch leaf Vspring to be heldvsubstantially axially of 'the'well when in detonating position, anddetonating leads `cormecting said explosive element to said detona'iingcable. Y

4. A Vstring of explosive charges arranged tobe run into a 'deep welland 'to bypass a partial obstruction present therein, said stringcomprising a supporting' and detonating cable, each explosive charge'including a leaf spring o'f greater length than the diameter of thedeep Well, said leafl spring `being secured at one end Yto saidsupporting cable to normally extend somewhat radially therefrom andarranged to temporarily yield toward the cable axis as the obstinationis being bypassed and then return toward normal position, an `'explosiveelement secured midway of each leaf spring to be held substantiallyaxially of 'thefwell when in detonating position, and 'det'onating leadsconnecting said explosive element to 'said fdetonating cable, saiddetonating cable including a plurality of individual conductors, 'theexplosive charges being arranged ina plurality of groupings of Vone ormore.

5. A string of explosive charges arranged to be run into a deep wellVand'to bypass a partial obstruction present therein, said stringcomprising a supporting Vand detonating cable, each explosive chargeincluding a leaf spring of greater length than the diameter of thede'epwell, said leaf spring being secured 'at one end'to saidsup-v portingcable to normally extend somewhat radially therefrom 'and arranged-totemporarily yield 4toward the cable axis as the obstruction is beingbypassed andthen return toward norrnal position, an explosive elementsecured midway of each leaf spring to be-held substantially axially ofthe well when in detonating position, and detonating leads connectingsaid explosive element to said detonating cable, said detonating cableincluding a plurality of individual conductors, the explosive chargesbeing arranged ina plurality off groupings of 'one or more, eachindividual c'ablercondnctor being connected vto a particular groupingonly.4 v Y r6. lA `string of explosivefc'ha'rges arranged-to be run intoa deep Awell 'and 'to bypass a partial obstruction present therein,s'ai'd k'string comprising a supporting Vand detoaV nating cable, cachexplosive `charge including -a leaf spring of greater `length 'than 'thediameter of the deep well, said leaf spring being secured `at one end tosaid supporting cable tonormally extend somewhat radially therefrom andarranged to temporarily yield toward the cable axis as the obstructionis being bypassed and then return toward normal position, an explosiveelement secured midway of each leaf spring to be held substantiallyaxially of 'the well when in detonating position, and detonating leadsconnecting said explosive element to said dctonating cable, saiddetonating cable including a ,plurality of individual conductors, theexplosive charges being arranged in a plurality of groupings of oneormore,` eachV individual -c-able conductor being connected to particulargroupingonly, and means for successively completing a detonating circuitthrough each individual cable conductor in a predetermined periodicity.

7. A stringof explosive charges `arranged to Abe run into a deep 'welland means arranged to detonate each explosive charge 'in a predeterminedsequence so that the explosion of said charges will produce a series ofshock Waves time spaced so as to set up a well fluid stimulatingApulsation in the well1 said string including a detonating andsupporting cable, a plurality of individual explosive chargesspaccdralong said cable, each charge including an explosive element andmeans for supporting explosive element axially 'of the well, saidexplosive element supporting means including a spring lez-1f securedzit-one end to supporting cable and between its ends to one ot' saidexplosive charges.

i References Cited in the ille of this patent UNT-ED STATES ATENTS224,024 Mason Feb. 3, 1880 2,043,340 Tilbury et al. lune 9, 19362,062,974 Lane Dec. 1, 1936 2,177,886 Y Halliburton -2 Oct. 3l, 19392,331,058 Stick Oct. 5, 1943 2,362,829 Kinley y Nov. v14, v19442,402,153 Elliott June 18, 1946 2,414,349 Alexander Jan. 14, 19472,450,366 Williams Sept. 28, 1948 2,599,245 Finn June 3, 1952 FORElGNPATENTS 3,659 Great Britain of 1879

